On Nutrition

Coronavirus. It’s all anyone can talk about right now, especially those of us who live in Washington state — which has become the national epicenter of the virus outbreak. But even if you’re working from home, canceling your social calendar, avoiding public spaces and washing your hands like you never have before, it’s natural to want to do more to protect yourself and your loved ones. One question I’ve been hearing a lot is, “How can I boost my immune system so I’m less likely to get sick?” You may or may not like the answer.

Your immune system has healthy limits

First, the bad news: You can’t “rev up” your immune system, and you wouldn’t want to. What you want to do is to support your immune system so it can function normally, and that’s not the same thing as boosting or supercharging it. If your immune system was actually operating at a higher level than “normal,” you would be at risk of developing an autoimmune disease, such as celiac disease, rheumatoid arthritis, inflammatory bowel disease, lupus, type 1 diabetes or thyroid disease. When your immune system is overactive, it can attack your body’s own tissues. Again, you don’t want that.

Before I move on to how you can support your immune system so it can better support you, I want to make one more thing clear: There are a lot of people out there who are selling products and diet plans that allegedly prevent and/or cure coronavirus. Some are well intentioned, yet misinformed. Others are out-and-out hucksters looking to exploit your fear. Either way, please don’t fall for it.

Going with your gut

You can eat to support your immune system, and ideally you were already doing so long before schools, employers and public health officials were advising us to stay home. But, as I often say: When it comes to eating to support your health and well-being, the earlier the better, but better late than never. One step is to choose foods that support a healthy gut.

About 80 percent of your body’s immune cells live in your gut, or intestine. The population of bacteria and other microbes — roughly 100 trillion — that make up your gut microbiota play a big role in the strength of your immune system. One of the many things that shapes your gut microbiota is the food you eat. Specifically, foods that contain probiotics or prebiotics.

Probiotics are bacteria and other microbes that have been shown to benefit our health when we consume enough of them. However, don’t go out and take a probiotic supplement, because different bacterial and microbial strains have different effects, so taking the wrong one could work against you. Instead, include foods that naturally contain probiotic microbes, such as yogurt and kefir. Prebiotics are foods containing fiber that the good bacteria in your gut like to eat, which helps them survive and thrive.

Immune-supporting nutrients

What about vitamins? Yes, there are certain nutrients that play a role in our immune function — notably vitamins A, C and D and the mineral zinc — but megadosing with oral supplements or an IV drip is not the answer, as there’s no evidence that higher doses are better. The immune system is complex, involving many cells and organs, and the way nutrients interact with our immune system and each other is also complex.

The one exception is vitamin D. It’s not something we get much of from food — fortified foods, fatty fish and some mushrooms are the main sources — and you’re probably not spending enough time outside with bare skin for your body to produce its own from exposure to the sun’s UV rays. One of vitamin D’s many roles in the body is supporting the immune system, and vitamin D deficiency is associated with increased risk of infections. A 2017 review from the World Health Organization found that although much more research is needed, it appears that taking a daily vitamin D supplement may decrease the risk of respiratory tract infections. How much to take? That’s unclear, but 800 to 1,000 IU per day is probably safe and sufficient.

Putting it all together

A plant-based diet with lots of brightly colored fruits and vegetables, along with beans, lentils, whole grains, nuts and seeds, will supply your beneficial gut microbes with plenty of prebiotic fiber and supply you with immune-supporting nutrients. If you’re trying to limit trips to the store, frozen fruits and vegetables are just as nutritious and easier to stock up on. Limit your intake of alcohol, sugar and highly processed foods, as they aren’t good for gut health and may displace more nutritious foods in your diet.

Keep moving. Even if you decide to forgo your usual gym routine or fitness class to reduce chances of exposure to SARS-CoV-2, the novel coronavirus, it’s important to find ways to stay active, because research shows that physical activity is good for the immune system. A few caveats: If you don’t currently exercise, start slowly, and if you do exercise regularly, there’s no evidence that upping the intensity of your workouts will offer you additional protection. So stay the course.

Protect your sleep. Research shows that adequate quality sleep helps maintain immune health, including reducing the risk of infectious diseases and supporting recovery if we do get sick.

Try to relax. Stress lowers your immune function and increases the risk of catching an infectious disease. Whether COVID-19 — the illness caused by the novel coronavirus — has you scared, or you’re taking the unfolding events in stride, try to find ways to manage the stress in your life in healthy ways.

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Carrie Dennett: CarrieOnNutrition@gmail.com;on Twitter: @CarrieDennett.Carrie Dennett, MPH, RDN, CD is a registered dietitian nutritionist at Nutrition By Carrie, and author of "Healthy For Your Life: A holistic approach to optimal wellness." Visit her at nutritionbycarrie.com.